Base station

ABSTRACT

A base station communicates with a user device transmitting an uplink signal based on a single-carrier transmission scheme. The base station includes a frequency hopping determining unit configured to determine whether to apply frequency hopping to the user device based on radio-wave propagation information from the user device and a traffic type of data to be transmitted by the user device; a scheduler configured to allocate frequencies to the user device based on uplink channel reception conditions of the user device; and a reporting unit configured to report allocation information indicating resource units allocated by the scheduler to the user device. When the frequency hopping determining unit determines to apply the frequency hopping to the user device, the scheduler allocates, to the user device, resource units with different frequency bands in different slots.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of application U.S. patentapplication Ser. No. 12/672,584, filed on Feb. 8, 2010,, which is anational stage application of PCT/JP2008/064540, filed Aug. 13, 2008,which claims priority to Japanese Patent Application No. 2007-211598,,filed Aug. 14, 2007. The priority application is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

The present invention generally relates to a radio communication system.More particularly, the present invention relates to a base station.

BACKGROUND ART

A successor communication system to W-CDMA and HSDPA, i.e., Long TermEvolution (LTE), is currently being discussed by 3GPP, a standardizationgroup for W-CDMA. In LTE, orthogonal frequency division multiplexing(OFDM) is to be used as a downlink radio access method andsingle-carrier frequency division multiple access (SC-FDMA) is to beused as an uplink radio access method (see, for example, 3GPP TR 25.814,(V7.0.0), “Physical Layer Aspects for Evolved UTRA,” June 2006).

In OFDM, a frequency band is divided into multiple narrow frequencybands (subcarriers) and data are transmitted on the subcarriers. Thesubcarriers are densely arranged along the frequency axis such that theypartly overlap each other but do not interfere with each other. Thismethod enables high-speed transmission and improves frequencyefficiency.

In SC-FDMA, a frequency band is divided into multiple frequency bandsand the frequency bands are allocated to different terminals fortransmission in order to reduce interference between the terminals.Also, SC-FDMA reduces variation of the transmission power and thereforemakes it possible to reduce power consumption of terminals and toachieve wide coverage.

A reference signal for uplink in E-UTRA indicates a pilot channel thatis used for purposes such as synchronization, channel estimation forcoherent detection, and measurement of received SINR in transmissionpower control. The reference signal is a transmission signal known tothe receiving end, i.e., the base station and is embedded at certainintervals in subframes.

SC-FDMA used as an uplink radio access method in E-UTRA is describedbelow with reference to FIG. 1. In SC-FDMA, a system frequency band isdivided into multiple resource blocks each including one or moresubcarriers. Each user device (user equipment: UE) is allocated one ormore resource blocks. In frequency scheduling, to improve thetransmission efficiency or the throughput of the entire system, resourceblocks are allocated preferentially to user devices with good channelconditions according to received signal quality or channel qualityindicators (CQIs) measured and reported based on downlink pilot channelsfor the respective resource blocks by the user devices. Also for uplinkradio access in E-UTRA, use of frequency hopping, where allocation offrequency blocks is varied according to a frequency hopping pattern, isbeing discussed.

In FIG. 1, time and frequency resources allocated to different userdevices are represented by different hatchings. For example, arelatively wide frequency band is allocated to UE2 in the firstsubframe, but a relatively narrow frequency band is allocated to UE2 inthe next subframe. Different frequency bands are allocated to the userdevices without overlapping.

In SC-FDMA, different time and frequency resources are allocated to userdevices in a cell for transmission to achieve orthogonality between theuser devices in the cell. Here, the minimum unit of the time andfrequency resources is called a resource unit (RU). In SC-FDMA, aconsecutive frequency band is allocated to each user to achievesingle-carrier transmission with a low peak-to-average power ratio(PAPR). Allocation of the time and frequency resources in SC-FDMA isdetermined by a scheduler of a base station based on propagationconditions of user devices and the quality of service (QoS) of data tobe transmitted. The QoS includes a data rate, a desired error rate, anda delay. Thus, in SC-FDMA, the system throughput is improved byallocating time and frequency resources providing good propagationconditions to respective user devices.

Base stations in a system independently determine allocation of time andfrequency resources. Therefore, a frequency band allocated in a cell mayoverlap a frequency band allocated in a neighboring cell. If frequencybands allocated in neighboring cells partly overlap each other, signalsinterfere with each other and their quality is reduced.

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

As described above, use of frequency hopping for uplink radio access inE-UTRA is being discussed.

However, configurations or methods for signaling a frequency hoppingpattern and/or allocated resource units in frequency hopping have notbeen discussed yet.

One object of the present invention is to provide a base station thatmakes it possible to use frequency hopping for uplink radio access in anE-UTRA system.

Means for Solving the Problems

In an aspect of this disclosure, there is provided a base stationcommunicating with a user device transmitting an uplink signal based ona single-carrier transmission scheme. The base station includes afrequency hopping determining unit configured to determine whether toapply frequency hopping to the user device based on radio-wavepropagation information from the user device and a traffic type of datato be transmitted by the user device; a scheduler configured to allocatefrequencies to the user device based on uplink channel receptionconditions of the user device; and a reporting unit configured to reportallocation information indicating resource units allocated by thescheduler to the user device. When the frequency hopping determiningunit determines to apply the frequency hopping to the user device, thescheduler is configured to allocate, to the user device, resource unitswith different frequency bands in different slots.

Advantageous Effect of the Invention

One aspect of the present invention provides a base station that makesit possible to use frequency hopping for uplink radio access in anE-UTRA system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing illustrating single-carrier FDMA;

FIG. 2 is a drawing illustrating a radio communication system accordingto an embodiment of the present invention;

FIG. 3 is a drawing illustrating exemplary mapping of uplink controlchannels;

FIG. 4 is a drawing illustrating exemplary allocation of resource unitsto user devices to which frequency hopping is applied;

FIG. 5 is a partial block diagram of a base station according to anembodiment of the present invention;

FIG. 6 is a partial block diagram of a user device according to anembodiment of the present invention;

FIG. 7 is a drawing illustrating exemplary allocation of resource unitsto user devices to which frequency hopping is applied;

FIG. 8 is a drawing illustrating exemplary allocation of resource unitsto user devices to which frequency hopping is applied;

FIG. 9 is a drawing illustrating exemplary allocation of resource unitsto user devices to which frequency hopping is applied;

FIG. 10 is a drawing illustrating exemplary allocation of resource unitsto user devices to which frequency hopping is applied;

FIG. 11 is a partial block diagram of a base station according to anembodiment of the present invention;

FIG. 12 is a partial block diagram of a user device according to anembodiment of the present invention;

FIG. 13 is a drawing illustrating exemplary allocation of resource unitsto user devices to which frequency hopping is applied; and

FIG. 14 is a drawing illustrating exemplary allocation of resource unitsto user devices to which frequency hopping is applied.

EXPLANATION OF REFERENCES

-   -   50 _(k), (50 ₁, 50 ₂, . . . , 50 _(k)) Cell    -   100 _(n), (100 ₁, 100 ₂, 100 ₃, . . . , 100 _(n)) User device    -   102 OFDM signal demodulation unit    -   104 Uplink-scheduling-grant-signal demodulation/decoding unit    -   106 Other-control-and-data-signals demodulation/decoding unit    -   108 Demodulation RS generating unit    -   110 Channel coding unit    -   112 Data modulation unit    -   114 SC-FDMA modulation unit    -   116 Broadcast-channel demodulation/decoding unit    -   200 _(n), (200 ₁, 200 ₂, 200 ₃, . . . , 200 _(m)) Base station    -   202 OFDM signal generating unit    -   204 Uplink-scheduling-grant-signal-transmission-control-signal        generating unit    -   206 Demodulation RS generating unit    -   208 Synchronization-detection/channel-estimation unit    -   210 Channel decoding unit    -   212 Coherent detection unit    -   214 Uplink-channel-condition estimation unit    -   216 Scheduler    -   218 Frequency hopping determining unit    -   220 Broadcast channel generating unit    -   400 Core network    -   500 Physical uplink shared channel    -   510 Uplink control channel    -   520 Uplink control channel

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are described below with referenceto the accompanying drawings. Throughout the accompanying drawings, thesame reference numbers are used for parts having the same functions, andoverlapping descriptions of those parts are omitted.

A radio communication system 1000 including user devices and basestations according to an embodiment of the present invention isdescribed below with reference to FIG. 2. In the present application,user devices (user equipment: UE) may also be called mobile stations.

The radio communication system 1000 is based on, for example, EvolvedUTRA and UTRAN (also called Long Term Evolution or Super 3G). The radiocommunication system 1000 includes base stations (eNode B: eNB) 200_(m), (200 ₁, 200 ₂, 200 ₃, . . . , 200 _(m); m is an integer greaterthan 0) and user devices 100 _(n), (100 ₁, 100 ₂, 100 ₃, . . . , 100_(n); n is an integer greater than 0) that communicate with the basestations 200 _(m). The base stations 200 _(m), are connected to an uppernode such as an access gateway 300 and the access gateway 300 isconnected to a core network 400. Each of the user devices 100 _(n), isin one of cells 50 _(k), (50 ₁, 50 ₂, . . . , 50 _(k); k is an integergreater than 0) and communicates with the corresponding one of the basestations 200 _(m), according to Evolved UTRA and UTRAN.

Here, it is assumed that some of the user devices 100 _(n), have alreadyestablished communication channels with the base stations 200 _(m), andare in communications; and the other user devices 100 _(n), have notestablished communication channels with the base stations 200 _(m), andare not in communications.

Each of the base stations 200 _(m), transmits synchronization signals.Each of the user devices 100 _(n) is located in one of the cells 50_(k), (50 ₁, 50 ₂, . . . , 50 _(k); k is an integer greater than 0).When the user device 100 _(n) is, for example, turned on or in theintermittent reception mode during communications, the user device 100_(n), performs a cell search based on the synchronization signals tofind a cell that provides good radio communication quality for the userdevice 100 _(n). More specifically, the user device 100 _(n), detects asymbol timing and a frame timing and detects cell-specific controlinformation such as a cell ID (or a scrambling code unique to a cellgenerated from the cell ID) or a group of cell IDs (hereafter called acell ID group) based on the synchronization signals.

A cell search may be performed when the user device 100 _(n), is incommunications as well as when the user device 100 _(n), is not incommunications. For example, the user device 100 _(n), performs a cellsearch during communications to find a cell using the same frequency orto find a cell using a different frequency. The user device 100 _(n),also performs a cell search when it is not in communications, forexample, when the user device 100 _(n), has just been turned on or is inthe standby mode.

The base stations 200 _(m), (200 ₁, 200 ₂, 200 ₃, . . . , 200 _(m)) havethe same configuration and functions and are therefore called the basestation 200, the base station 200 _(m), or the base stations 200 _(m),in the descriptions below unless otherwise mentioned. The user devices100 _(n), (100 ₁, 100 ₂, 100 ₃, . . . 100 _(n)) have the sameconfiguration and functions and are therefore called the user device100, the user device 100 _(n), or the user devices 100 _(n), in thedescriptions below unless otherwise mentioned. The cells 50 _(k), (50 ₁,50 ₂, 50 ₃, . . . , 50 _(k)) have the same configuration and functionsand are therefore called the cell 50 _(k), or the cells 50 _(k), in thedescriptions below unless otherwise mentioned.

In the radio communication system 1000, orthogonal frequency divisionmultiplexing (OFDM) is used as the downlink radio access method andsingle-carrier frequency division multiple access (SC-FDMA) is used asthe uplink radio access method. In OFDM, as described above, a frequencyband is divided into narrow frequency bands (subcarriers) and data aretransmitted on the subcarriers. In SC-FDMA, a frequency band is dividedinto multiple frequency bands and the frequency bands are allocated todifferent user devices for transmission in order to reduce interferencebetween the user devices.

Communication channels used in Evolved UTRA and UTRAN are describedbelow.

For downlink, a physical downlink shared channel (PDSCH) shared by theuser devices 100 _(n), and an LTE downlink control channel are used. Indownlink, the LTE downlink control channel is used to report informationon user devices to be mapped to the physical downlink shared channel,transport format information for the physical downlink shared channel,information on user devices to be mapped to a physical uplink sharedchannel, transport format information for the physical uplink sharedchannel, and acknowledgement information for the physical uplink sharedchannel; and the physical downlink shared channel is used to transmituser data.

Also in downlink, the base stations 200 _(m) transmit synchronizationsignals used by the user devices 100 _(n), to perform cell searches.

For uplink, a physical uplink shared channel (PUSCH) shared by the userdevices 100 _(n), and an LTE uplink control channel are used. There aretwo types of uplink control channels: the first is an uplink controlchannel to be time-division-multiplexed with the physical uplink sharedchannel, and the second is an uplink control channel to befrequency-division-multiplexed with the physical uplink shared channel.In uplink, the LTE uplink control channel is used to report downlinkchannel quality indicators (CQI) used for scheduling and adaptivemodulation and coding (AMC) of the physical downlink shared channel andto report acknowledgement information (HARQ ACK information) for thephysical downlink shared channel.

An “uplink channel” may indicate either the physical uplink sharedchannel or the LTE uplink control channel. There are two types of LTEuplink control channels: the first is an uplink control channel to betime-division-multiplexed with the physical uplink shared channel, andthe second is an uplink control channel to befrequency-division-multiplexed with the physical uplink shared channel.FIG. 3 is a drawing illustrating exemplary mapping of LTE uplink controlchannels.

As shown in FIG. 3, frequency-division-multiplexed uplink controlchannels are mapped to different positions in two slots of a subframe(frequency hopping is applied to the uplink control channels). In FIG.3, 500 indicates a physical uplink shared channel, 510 indicates uplinkcontrol channels that are frequency-division-multiplexed with thephysical uplink shared channel, and 520 indicates uplink controlchannels that are time-division-multiplexed with the physical uplinkshared channel.

In uplink, the LTE uplink control channel is used to report downlinkchannel quality indicators (CQI) used for scheduling and adaptivemodulation and coding (AMC) of the physical downlink shared channel andto transmit acknowledgement information (HARQ ACK information) for thephysical downlink shared channel; and the physical uplink shared channelis used to transmit user data.

A transport channel to be mapped to the physical uplink shared channelis an uplink shared channel (UL-SCH). User data are mapped to theUL-SCH.

The physical uplink control channel may also be used to transmit, inaddition to the CQI and the acknowledgement information, a schedulingrequest for requesting allocation of resources of an uplink sharedchannel and a release request used in persistent scheduling. Here,allocation of resources of an uplink shared channel indicates a processwhere a base station reports to a user device by using the physicaldownlink control channel in a given subframe that the user device isallowed to communicate using the uplink shared channel in a subsequentsubframe.

In the radio communication system of this embodiment, frequency hoppingis used for uplink. In frequency hopping, allocation of frequency blocksis varied according to a frequency hopping pattern.

As shown in FIG. 4, when frequency hopping is used for uplink, resourcesare allocated to the user device 100 _(n), by resource units (RU). InFIG. 4, the horizontal axis indicates frequency and the vertical axisindicates time. For example, one resource unit has a bandwidth of 180,kHz and one slot has a length of 0.5 ms. One subframe includes twoslots.

Frequency bands located near the lower and higher ends of a systemfrequency band may be allocated to user devices to which frequencyhopping is applied. This makes it possible to increase the frequencydiversity among user devices to which frequency hopping is applied.Frequency bands other than the frequency bands near the lower and higherends of the system frequency band are allocated to user devices to whichlocalized FDMA is applied. For the user devices to which localized FDMAis applied, this improves the compatibility with the single-carriertransmission scheme.

The base station 200 _(m), of this embodiment determines whether toapply frequency hopping to a user device based on propagationinformation and a traffic type of the user device. The propagationinformation of a user device includes the moving speed of the userdevice. For example, the base station 200 _(m), determines to applyfrequency hopping to a user device if it is expected that applyingfrequency hopping to the user device achieves frequency diversity gain.More specifically, the base station 200 _(m), determines to applyfrequency hopping to a user device moving at high speed or a user deviceperiodically transmitting small-sized data such as voice packets (VoIPpackets). After determining to apply frequency hopping to a user device,the base station 200 _(m), reports to the user device that an uplinksignal is transmitted to the user device by frequency hopping.

In scheduling, to the user device to which frequency hopping is to beapplied, the base station 200 _(m), allocates resource units withdifferent frequency bands in different slots of each subframe. In otherwords, a subframe is divided in the time direction into a first half(first slot) and a second half (second slot), and a first resourceunit(s) allocated in the first half (first slot) of the subframe has afrequency band that is different from the frequency band of a secondresource unit(s) allocated in the second half (second slot) of thesubframe.

After scheduling, the base station 200 _(m) reports informationindicating the allocated resource units via an uplink scheduling grantto the user device. For example, the base station 200 _(m), reports, foreach subframe, a first resource unit(s) and the amount of shift in thefrequency direction from the first resource unit(s).

Next, the base station 200 _(m), of this embodiment is described withreference to FIG. 5.

The base station 200 _(m), of this embodiment includes an OFDM signalgenerating unit 202, anuplink-scheduling-grant-signal-transmission-control-signal generatingunit 204, a demodulation RS generating unit 214, asynchronization-detection/channel-estimation unit 208, a channeldecoding unit 210, a coherent detection unit 212, anuplink-channel-condition estimation unit 214, a scheduler 216, and afrequency hopping determining unit 218. The OFDM signal generating unit202 and the uplink-scheduling-grant-signal-transmission-control-signalgenerating unit 204 constitute a transmitting unit. The demodulation RSgenerating unit 214, the synchronization-detection/channel-estimationunit 208, the channel decoding unit 210, the coherent detection unit212, the uplink-channel-condition estimation unit 214, the scheduler216, and the frequency hopping determining unit 218 constitute areceiving unit.

Uplink channels received from the user devices 100 _(n), are input tothe synchronization-detection/channel-estimation unit 208, the coherentdetection unit 212, and the uplink-channel-condition estimation unit214.

The synchronization-detection/channel-estimation unit 208 performssynchronization detection for the input received signals to estimatetheir reception timings, performs channel estimation based on ademodulation reference signal input from the demodulation RS generatingunit 206 described later, and inputs the channel estimation results tothe coherent detection unit 212.

The coherent detection unit 212 performs coherent detection for thereceived signals based on the channel estimation results and allocatedfrequencies and bandwidths input from the scheduler 216 described later,and inputs the demodulated received signals to the channel decoding unit210. The channel decoding unit 210 decodes the demodulated receivedsignals and generates reproduced data signals corresponding to usernumbers of selected user devices 100, input from the scheduler 216. Thegenerated reproduced data signals are transmitted to a network.

The uplink-channel-condition estimation unit 214 estimates uplinkchannel conditions of the user devices 100 _(n), based on the inputreceived signals and inputs the estimated uplink channel conditions tothe scheduler 216.

The frequency hopping determining unit 218 receives propagationinformation and traffic types of the user devices 100 _(n). Based on thereceived propagation information and traffic types of the user devices100 _(n), the frequency hopping determining unit 218 determines whetherto apply frequency hopping to the user devices 100. For example, if thepropagation information of a user device indicates that the moving speedof the user device is greater than or equal to a predetermined thresholdor if the traffic type is small-sized data such as voice packets (VoIPpackets) that are transmitted periodically, the frequency hoppingdetermining unit 218 determines to apply frequency hopping to the userdevice. Meanwhile, if the propagation information of a user deviceindicates that the moving speed of the user device is less than thepredetermined threshold or if the traffic type is other than small-sizeddata such as voice packets (VoIP packets) that are transmittedperiodically, the frequency hopping determining unit 218 determines tonot apply frequency hopping to the user device. After determining toapply frequency hopping to one or more user devices 100 _(n), thefrequency hopping determining unit 218 reports to the scheduler 216 andthe uplink-scheduling-grant-signal-transmission-control-signalgenerating unit 204 that frequency hopping is to be applied to the userdevices 100 _(n).

The scheduler 216 performs, for example, frequency scheduling based onthe estimated uplink channel conditions of the user devices 100 _(n),and QoS information of the user devices 100 _(n), such as requested datarates, buffer statuses, desired error rates, and delays. Then, thescheduler 216 inputs allocated frequencies and bandwidths to theuplink-scheduling-grant-signal-transmission-control-signal generatingunit 204 and the coherent detection unit 212, and inputs user numbers ofselected user devices 100 _(n), to theuplink-scheduling-grant-signal-transmission-control-signal generatingunit 204 and the channel decoding unit 210. Here, “scheduling” indicatesa process of selecting user devices allowed to transmit packet datausing a shared channel in a given subframe. After user devices areselected in the scheduling, modulation schemes, coding rates, and datasizes of packet data to be transmitted by the selected user devices aredetermined. The modulation schemes, coding rates, and data sizes aredetermined, for example, based on SIRS of sounding reference signals(SRS) transmitted from the user devices via uplink. Also, resource unitsto be used by the selected user devices to transmit the packet data aredetermined. The resource units are determined, for example, based onSIRs of sounding reference signals (SRS) transmitted from the userdevices via uplink.

The uplink-scheduling-grant-signal-transmission-control-signalgenerating unit 204 generates uplink scheduling grants based on thescheduling results, determined transport formats, and allocatedfrequency resources. Each uplink scheduling grant, for example, includesan ID of the selected user device allowed to communicate using thephysical uplink shared channel, transport format information for theuser data such as a data size and a modulation scheme, uplink resourceunit allocation information, and transmission power information for theuplink shared channel. Here, uplink resource units correspond tofrequency resources and may also be called resource blocks.

When user devices (hereafter may be called frequency-hopping-applieduser devices) to which frequency hopping is to be applied are reportedfrom the frequency hopping determining unit 218, the scheduler 216allocates, to each of the frequency-hopping-applied user devices,resource units with different frequency bands in different slots of eachsubframe.

Also, the uplink-scheduling-grant-signal-transmission-control-signalgenerating unit 204 reports to the frequency-hopping-applied userdevices that frequency hopping is to be applied. This “frequency hoppingreport” may be sent via the uplink scheduling grant or via anupper-layer control signal. The uplink scheduling grant is transmittedevery subframe. Therefore, compared with a case using an upper-layercontrol signal, sending the frequency hopping report via the uplinkscheduling grant makes it possible to more quickly switch between normaland frequency hopping allocation schemes.

When frequency hopping is to be applied to a user device, theuplink-scheduling-grant-signal-transmission-control-signal generatingunit 204 generates, for each subframe, an uplink scheduling grantincluding information indicating first resource units (allocated in thefirst half (first slot) of the subframe) and the amount of shift in thefrequency direction from the first resource units. For example, assumingthat indexes are assigned to resource units from one end of thefrequency direction, theuplink-scheduling-grant-signal-transmission-control-signal generatingunit 204 generates, for each subframe, an uplink scheduling grantincluding indexes of first resource units and the amount of shift fromthe indexes of the first resource units. The user device 100 _(n)determines second resource units allocated in the second half (secondslot) of the subframe based on the amount of shift in the frequencydirection from the first resource units.

The demodulation RS generating unit 206 generates a demodulationreference signal and inputs the generated demodulation reference signalto the synchronization-detection/channel-estimation unit 208.

The uplink-scheduling-grant-signal-transmission-control-signalgenerating unit 204 generates a control signal(uplink-scheduling-grant-signal transmission control signal) includingthe allocated frequencies and bandwidths and the user numbers of theselected user devices received from the scheduler 216, and inputs thecontrol signal to the OFDM signal generating unit 202. The controlsignal may include the uplink scheduling grants.

The OFDM signal generating unit 204 generates an OFDM signal includingthe control signal and inputs the OFDM signal to a radio transmitter. Asa result, the control signal is transmitted to the selected user devicesvia a downlink control channel.

The OFDM signal generating unit 202 may generate an OFDM signal thatincludes, in addition to the above described control channel, downlinkchannels such as a downlink reference signal, a data channel, and apaging channel, and input the OFDM signal to the radio transmitter. As aresult, the downlink channels are transmitted to the users.

Next, the user device 100 _(n), of this embodiment is described withreference to FIG. 6.

The user device 100 _(n), of this embodiment includes an OFDM signaldemodulation unit 102, an uplink-scheduling-grant-signaldemodulation/decoding unit 104, an other-control-and-data-signalsdemodulation/decoding unit 106, a demodulation RS generating unit 108, achannel coding unit 110, a data modulation unit 112, and an SC-FDMAmodulation unit 114. The OFDM signal demodulation unit 102, theuplink-scheduling-grant-signal demodulation/decoding unit 104, and theother-control-and-data-signals demodulation/decoding unit 106 constitutea receiving unit. The demodulation RS generating unit 108, the channelcoding unit 110, the data modulation unit 112, and the SC-FDMAmodulation unit 114 constitute a transmitting unit.

The user device 100 _(n), decodes an uplink scheduling grant signal andif a user number corresponding to the user device 100 _(n), is includedin the uplink scheduling grant signal, generates and transmits atransmission signal.

A received signal from the base station 200 _(m) is input to the OFDMsignal demodulation unit 102. The OFDM signal demodulation unit 102demodulates the received signal, inputs anuplink-scheduling-grant-signal transmission control signal in thereceived signal to the uplink-scheduling-grant-signaldemodulation/decoding unit 104, and inputs control and data signalsother than the uplink-scheduling-grant-signal transmission controlsignal in the received signal to the other-control-and-data-signalsdemodulation/decoding unit 106.

The uplink-scheduling-grant-signal demodulation/decoding unit 104demodulates and decodes the uplink scheduling grant signal. If theuplink scheduling grant signal includes a “frequency hopping report”indicating that frequency hopping is applied to the user device 100_(n), the uplink-scheduling-grant-signal demodulation/decoding unit 104inputs the frequency hopping report to the SC-FDMA modulation unit 114.The uplink-scheduling-grant-signal demodulation/decoding unit 104 alsoinputs information indicating allocated resource units to the SC-FDMAmodulation unit 114. For example, the uplink-scheduling-grant-signaldemodulation/decoding unit 104 inputs, to the SC-FDMA modulation unit114, information indicating first resource units allocated in a firstslot of each subframe and the amount of shift in the frequency directionfrom the first resource units.

The demodulation RS generating unit 108 generates a demodulationreference signal and inputs the generated demodulation reference signalto the SC-FDMA modulation unit 114.

Meanwhile, the channel coding unit 110 performs channel coding on userdata, and the data modulation unit 112 performs data modulation on thechannel-coded user data and inputs the data-modulated user data to theSC-FDMA modulation unit 114.

The SC-FDMA modulation unit (DFT-spread OFDM) 114 modulates the inputdemodulation reference signal and the user data based on the allocatedresource units and outputs a transmission signal. For example, theSC-FDMA modulation unit (DFT-spread OFDM) 114 determines second resourceunits allocated in the second slot of a subframe based on the amount ofshift in the frequency direction from the first resource units. Thisconfiguration makes it possible for a user device to which frequencyhopping is applied to transmit data using resource units with differentfrequency bands in different slots of each subframe.

Next, a radio communication system including base stations and userdevices according to another embodiment of the present invention isdescribed.

The configurations of the radio communication system, the base stations,and the user devices of this embodiment are substantially the same asthose described with reference to FIGS. 2, 5, and 6.

In this embodiment, similar to the above described embodiment, the basestation 200 allocates, to a user device to which frequency hopping is tobe applied, resource units with different frequency bands in differentslots of each subframe. In this embodiment, the amount of shift in thefrequency direction from first resource units allocated in the firsthalf of each subframe is predetermined and used to determine secondresource units allocated in the second half of the subframe. Forexample, assuming that indexes are assigned to resource units from oneend of the frequency direction, the amount of shift is represented by adifference between the indexes (resource unit numbers) of first andsecond resource units. In the example shown in FIG. 7, the amount ofshift is +21, and second resource units are identified by resource unitnumbers obtained by adding 21, to each of the resource unit numbers offirst resource units. The amount of shift may be defined inspecifications according to a frequency band supported by user devicesor may be reported via an upper layer signal. This configuration allowsa user device to transmit a signal in a second slot of a subframe usinga frequency band that differs by a given amount from the frequency bandused in a first slot of the subframe, and thereby makes it possible toachieve a certain frequency diversity gain.

After scheduling, the base station 200 reports information indicatingallocated resource units via an uplink scheduling grant to the userdevice. Because the amount of shift is predetermined or has beenreported via an upper layer, the base station 200 reports, for eachsubframe, indexes of the first resource units.

When user devices to which frequency hopping is to be applied(frequency-hopping-applied user devices) are reported from the frequencyhopping determining unit 218, the scheduler 216 allocates first resourceunits in the first half (first slot) of each subframe to thefrequency-hopping-applied user devices. Here, since SC-FDMA is employedfor uplink, when multiple resource units are to be allocated to a userdevice, it is necessary to allocate consecutive resource units in thefirst slot of each subframe so that resource units allocated in thesecond slot of the subframe do not become inconsecutive.

For a user device to which frequency hopping is to be applied, theuplink-scheduling-grant-signal-transmission-control-signal generatingunit 204 generates, for each subframe, an uplink scheduling grantincluding information, such as indexes, indicating first resource unitsallocated in the first half of the subframe.

Next, a radio communication system including base stations and userdevices according to another embodiment of the present invention isdescribed.

The configurations of the radio communication system, the base stations,and the user devices of this embodiment are substantially the same asthose described with reference to FIGS. 2, 5, and 6.

In this embodiment, similar to the above described embodiments, the basestation 200 allocates, to a user device to which frequency hopping is tobe applied, resource units with different frequency bands in differentslots of each subframe. Also in this embodiment, the correspondencebetween first resource units allocated in the first half of a subframeand second resource units allocated in the second half of the subframeis predetermined. For example, assuming that indexes are assigned toresource units from one end of the frequency direction and an index of afirst resource unit in the first half of a subframe is k (where k is aninteger greater than or equal to 0), a corresponding second resourceunit in the second half of the subframe is represented by “the highestresource unit index−k” as shown in FIG. 8. The correspondence may bedefined in specifications or may be reported via an upper layer signal.This configuration prevents resource units allocated in a second slotfrom becoming inconsecutive and thereby makes it possible to achievesingle-carrier transmission without performing any special controlprocess.

After scheduling, information indicating allocated resource units isreported via an uplink scheduling grant. Because the correspondencebetween first resource units and second resource units is predeterminedor has been reported via an upper layer, indexes of the first resourceunits is reported for each subframe via the uplink scheduling grant.

When user devices to which frequency hopping is to be applied(frequency-hopping-applied user devices) are reported from the frequencyhopping determining unit 218, the scheduler 216 allocates first resourceunits in the first half (first slot) of each subframe to thefrequency-hopping-applied user devices.

For a user device to which frequency hopping is to be applied, theuplink-scheduling-grant-signal-transmission-control-signal generatingunit 204 generates, for each subframe, an uplink scheduling grantincluding information, such as indexes, indicating the first resourceunits.

Next, a radio communication system including base stations and userdevices according to another embodiment of the present invention isdescribed.

The configurations of the radio communication system, the base stations,and the user devices of this embodiment are substantially the same asthose described with reference to FIGS. 2, 5, and 6.

In this embodiment, resource unit groups (RUG) each including multipleconsecutive resource units are defined.

Similar to the above described embodiments, the base station 200allocates, to a user device to which frequency hopping is to be applied,resource units with different frequency bands in different slots of eachsubframe. In this embodiment, the amount of shift in the frequencydirection from a first resource unit group in the first half (firstslot) of each subframe is predetermined and used to determine a secondresource unit group in the second half (second slot) of the subframe.For example, assuming that indexes are assigned to resource unit groupsfrom one end of the frequency direction, the amount of shift isrepresented by a difference between the indexes (resource unit groupnumbers) of first resource unit groups and second resource unit groups.In the example shown in FIG. 9, the amount of shift is +5, and a secondresource unit group #6, in the second slot of a subframe is identifiedby adding 5, to a resource unit group number #1, of the correspondingfirst resource unit group in the first slot of the subframe.

Also in this embodiment, the correspondence between resource units in afirst resource unit group and a second resource unit group may bepredetermined. Let us assume that indexes are assigned to resource unitsin each resource unit group from one end of the frequency direction asshown in FIG. 10. In this case, when an index of a resource unit in afirst resource unit group is i (where i is an integer, and 0<i≦number ofresource units in resource unit group), the corresponding resource unitin the second resource unit group is represented by “the highestresource unit index in the second resource unit group+1−i”. Thecorrespondence may be defined in specifications or may be reported viaan upper layer signal. This configuration allows a user device totransmit a signal in a second slot of a subframe using a frequency bandin a second resource unit group that differs by a given amount from thefrequency band in a first resource unit group used in a first slot ofthe subframe, and thereby makes it possible to achieve a certainfrequency diversity gain. This configuration also prevents resourceunits allocated in the second slot from becoming inconsecutive andthereby makes it possible to achieve single-carrier transmission withoutperforming any special control process.

After scheduling, information, such as indexes, indicating allocatedresource units is reported via an uplink scheduling grant. Because thecorrespondence between first and second resource unit groups and thecorrespondence between resource units in the first and second resourceunit groups are predetermined or have been reported via an upper layer,information indicating the first resource unit group and informationindicating resource units in the first resource unit group are reportedvia the uplink scheduling grant. More particularly, an index of thefirst resource unit group and indexes of resource units in the firstresource unit group are reported via the uplink scheduling grant.

When user devices to which frequency hopping is to be applied(frequency-hopping-applied user devices) are reported from the frequencyhopping determining unit 218, the scheduler 216 allocates first resourceunits in the first half (first slot) of each subframe to thefrequency-hopping-applied user devices.

For each of the frequency-hopping-applied user devices, theuplink-scheduling-grant-signal-transmission-control-signal generatingunit 204 generates, for each subframe, an uplink scheduling grantincluding an index of a first resource unit group allocated in the firsthalf of the subframe and indexes of resource units in the first resourceunit group.

Next, a radio communication system including base stations and userdevices according to another embodiment of the present invention isdescribed.

The configuration of the radio communication system of this embodimentis substantially the same as that described with reference to FIG. 2.

A base station 200 of this embodiment has a configuration as shown inFIG. 11 where a broadcast channel generating unit 220 connected to thescheduler 216 and the OFDM signal generating unit 202 is added to theconfiguration shown in FIG. 5.

In this embodiment, the scheduler 216 inputs allocation informationindicating resource units allocated in the scheduling to the broadcastchannel generating unit 220.

The broadcast channel generating unit 220 transmits a broadcast channelincluding the allocation information via a physical downlink sharedchannel. The broadcast channel transmitted via the physical downlinkshared channel is also called a dynamic broadcast channel.

This configuration makes it possible to report to a user device thatfrequency hopping is to be applied to the user device by using only onebit. In this case, the uplink scheduling grant includes one bit ofinformation indicating whether frequency hopping is to be applied.

A user device 100 of this embodiment has a configuration as shown inFIG. 12 where a broadcast-channel demodulation/decoding unit 116connected to the OFDM signal demodulation unit 102 and the SC-FDMAmodulation unit 114 is added to the configuration shown in FIG. 6.

A received signal from the base station 200 _(m) is input to the OFDMsignal demodulation unit 102. The OFDM signal demodulation unit 102demodulates the received signal, inputs anuplink-scheduling-grant-signal transmission control signal in thereceived signal to the uplink-scheduling-grant-signaldemodulation/decoding unit 104, inputs a broadcast channel in thereceived signal to the broadcast-channel demodulation/decoding unit 116,and inputs control and data signals other than theuplink-scheduling-grant-signal transmission control signal and thebroadcast channel in the received signal to theother-control-and-data-signals demodulation/decoding unit 106.

The broadcast-channel demodulation/decoding unit 116 demodulates anddecodes the input broadcast channel and inputs allocation information ofresource units to the SC-FDMA modulation unit 114.

In the above described embodiments, as shown in FIG. 13, frequency bandslocated near the lower and higher ends of a system frequency band areallocated to user devices to which frequency hopping is applied, andother frequency bands are allocated to user devices to which localizedFDMA is applied. In this embodiment, as shown in FIG. 14, frequencybands other than the frequency bands located near the lower and higherends of a system frequency band may also be allocated to user devices towhich frequency hopping is applied. With this configuration, it ispossible to efficiently perform frequency scheduling even when frequencyhopping is applied to a large number of user devices. system based onEvolved UTRA and UTRAN (also called Long Term Evolution or Super 3G) isused. However, a base station according to an embodiment of the presentinvention may also be applied to any system employing an FDMA scheme,such as SC-FDMA, for uplink.

Although specific values are used in the above descriptions tofacilitate the understanding of the present invention, the values arejust examples and different values may also be used unless otherwisementioned.

The present invention is not limited to the specifically disclosedembodiments, and variations and modifications may be made withoutdeparting from the scope of the present invention. Although functionalblock diagrams are used to describe apparatuses in the aboveembodiments, the apparatuses may be implemented by hardware, software,or a combination of them.

The invention claimed is:
 1. A user device, comprising: a modulationunit adapted for a system where multiple resource units are defined in asystem frequency band in a frequency domain, a subframe includes a firstslot and a second slot in a time domain, and each of the resource unitshas a length of one slot in the time domain, the modulation unit beingconfigured to map data of the user device to resource units withdifferent frequency bands in the first slot and the second slot; atransmission unit configured to transmit the mapped data; and areception unit, wherein two or more resource unit groups each includingtwo or more resource units that are consecutive in the frequency domainare defined in the system frequency band for each of the first slot andthe second slot, wherein the modulation unit is configured to map thedata to a first resource unit in a first resource unit group in thefirst slot and to a second resource unit in a second resource unit groupin the second slot such that the first resource unit group is apart fromthe second resource unit group by a bandwidth corresponding to apredetermined number of the resource unit groups, wherein indexes areassigned to the resource units in each of the resource unit groups, theindexes gradually increasing from 1 in a direction from a low frequencyside to a high frequency side, wherein the second resource unit in thesecond resource unit group to which the data are mapped in the secondslot is represented by a formula: (a highest index of the resource unitsin the second resource unit group) +1 −(an index of the first resourceunit in the first resource unit group to which the data are mapped inthe first slot), wherein the reception unit is configured to receive,from a base station, an uplink scheduling grant including informationindicating the first resource unit and information indicating that afrequency hopping is applied to the user device, and wherein themodulation unit is configured to map the data of the user device to thefirst and second resource units based on the received uplink schedulinggrant.
 2. A method performed by a user device for a system wheremultiple resource units are defined in a system frequency band in afrequency domain, a subframe includes a first slot and a second slot ina time domain, and each of the resource units has a length of one slotin the time domain, the method comprising: mapping data of the userdevice to resource units with different frequency bands in the firstslot and the second slot; and transmitting the mapped data, wherein twoor more resource unit groups each including two or more resource unitsthat are consecutive in the frequency domain are defined in the systemfrequency band for each of the first slot and the second slot, whereinthe data are mapped to a first resource unit in a first resource unitgroup in the first slot and to a second resource unit in a secondresource unit group in the second slot such that the first resource unitgroup is apart from the second resource unit group by a bandwidthcorresponding to a predetermined number of the resource unit groups,wherein indexes are assigned to the resource units in each of theresource unit groups, the indexes gradually increasing from 1 in adirection from a low frequency side to a high frequency side, whereinthe second resource unit in the second resource unit group to which thedata are mapped in the second slot is represented by a formula: (ahighest index of the resource units in the second resource unit group)+1 −(an index of the first resource unit in the first resource unitgroup to which the data are mapped in the first slot), wherein themethod further comprises receiving, from a base station, an uplinkscheduling grant including information indicating the first resourceunit and information indicating that a frequency hopping is applied tothe user device, and wherein, in the mapping, the data of the userdevice are mapped to the first and second resource units based on thereceived uplink scheduling grant.
 3. A communication system, comprising:a user device; and a base station, wherein the user device comprises: amodulation unit adapted for a system where multiple resource units aredefined in a system frequency band in a frequency domain, a subframeincludes a first slot and a second slot in a time domain, and each ofthe resource units has a length of one slot in the time domain, themodulation unit being configured to map data of the user device toresource units with different frequency bands in the first slot and thesecond slot; a transmission unit configured to transmit the mapped data;and a reception unit, wherein two or more resource unit groups eachincluding two or more resource units that are consecutive in thefrequency domain are defined in the system frequency band for each ofthe first slot and the second slot, wherein the modulation unit isconfigured to map the data to a first resource unit in a first resourceunit group in the first slot and to a second resource unit in a secondresource unit group in the second slot such that the first resource unitgroup is apart from the second resource unit group by a bandwidthcorresponding to a predetermined number of the resource unit groups,wherein indexes are assigned to the resource units in each of theresource unit groups, the indexes gradually increasing from 1 in adirection from a low frequency side to a high frequency side, whereinthe second resource unit in the second resource unit group to which thedata are mapped in the second slot is represented by a formula: (ahighest index of the resource units in the second resource unit group)+1 −(an index of the first resource unit in the first resource unitgroup to which the data are mapped in the first slot), wherein thereception unit is configured to receive, from the base station, anuplink scheduling grant including information indicating the firstresource unit and information indicating that a frequency hopping isapplied to the user device, and wherein the modulation unit isconfigured to map the data of the user device to the first and secondresource units based on the received uplink scheduling grant.